Even before the recent dramatic increases in the price of gold, there had been an effort by workers in the art to develop gold alloys having the appearance of 10, 12, 14, and 18 karat gold but with a much lower gold content. However, many problems have been encountered in achieving the desired durability, workability, corrosion and tarnish resistance and particularly in simulating the appearance of yellow gold alloys as the percentages of gold have been decreased to provide a lower cost substitute for 10 and higher karat gold. Representative of the efforts of prior art workers are the following patents, U.S. Pat. Nos. 2,141,156; 2,141,157; 2,200,050; 2,216,495; 2,248,100; 2,576,738; 2,654,146; 4,266,973; and 4,276,086. It can be noted that these efforts have all been directed to yellow gold alloys in the 8 to 20 karat range. For example, U.S. Pat. Nos. 2,141,156 and 2,141,157 to Peterson are directed to 8 to 14 karat gold alloys. U.S. Pat. No. 2,200,050 to Auwarter, U.S. Pat. No. 2,216,495, and U.S. Pat. No. 2,248,100 to Loebich are directed to gold alloys preferably in the 33-45% gold range or above 8 karats. U.S. Pat. Nos. 2,576,738 to Williams; 2,654,146 to Mooradian; 4,266,973 to Guzowski and 4,276,086 to Murao all deal principally in the 8 to 20 karat range.
The problems of providing a truly low cost substitute for 10 or higher karat gold having the desired color, hue and luster as well as other desirable properties such as resistance to corrosion and tarnishing as well as a reduction of surface roughness have heretofore not been overcome in the prior art. In particular, it has been observed that attempts to produce yellow gold alloys having a gold content in the 5 to 6 karat range have failed to produce an alloy having the color, hue and luster of known yellow gold alloys of 10 and higher karat while exhibiting the good corrosion resistance and surface smoothness also found in 10 or higher karat gold. Otherwise expressed, in the past unless the gold content of the alloy was above 35% of the total weight of the alloy the color, hue and luster thereof was unacceptable for use in the jewelrey industry. Although attempts have been made to produce a gold alloy for use in jewelry production having a gold content or less than 30%, the aesthetic appearance of such alloys has generally not been comparable to 10 and higher karat gold. For example, although prior art patents can be found which speak of the broad range of gold content (not the preferred range) as having a lower limit of 25% gold (about 6 karats) e.g., U.S. Pat. No. 2,200,050 to Auwarter, such alloys have been found to clearly lack the color, hue and luster of 10 or higher karat gold. In addition, the Auwarter alloy must contain 2-6% palladium which prevents the alloy from being electropolished. As a result, it would have to be hand polished which takes a considerable amount of time and effort and does not give the quality of an electro-polished alloy.